1. Field of the Invention
The present invention relates to a semiconductor device having a multilayer wiring structure and a method of manufacturing the semiconductor device, and more particularly, to an antireflection film of the semiconductor device.
2. Description of the Related Art
Up to now, an antireflection film has been formed to prevent halation which causes defect at the patterning of photo resist formed on an aluminum film or an aluminum alloy film. For example, a manufacturing method of depositing a nitrided refractory metal film made of TiN, TaN, ZrN, HfN, or the like by sputtering is described in JP 01-241162 A. FIGS. 7 to 11 show an example of a multilayer wiring manufacturing process using the nitrided refractory metal film as the antireflection film.
In the application of the nitrided refractory metal film as an antireflection film to a multilayer wiring structure, requirements are not limited to merely reduce reflectance. This is because, connection at low via resistance between a lower metal line and an upper metal line through a contact hole is quite important in a semiconductor device having the multilayer wiring structure.
Since it is difficult to obtain a sufficiently low contact resistance according to the aforementioned manufacturing method described in JP 01-241162 A, in order to solve the difficulty a manufacturing method of performing heat treatment in an atmosphere containing nitrogen after the deposition of a refractory metal film to reduce the resistivity of the refractory metal film is described in JP 05-226338 A, and a manufacturing method of stacking a Ti film and a TiN film is described in JP 05-190551 A. Main reason for the use of refractory metal for an antireflection film is to improve long-term reliability. Use of aluminum or an aluminum alloy for the major interconnection is accompanied by a deterioration phenomenon in the long-term reliability of the interconnection such as electromigration and stress migration. It has been widely known that a reinforcing effect in interconnection can be obtained by using the refractory metal to achieve a high durability to the deterioration phenomenon.
One of the features in the conventional techniques is that the nitrided refractory metal film is applied to the antireflection film for the semiconductor device having the multilayer wiring structure. Application of the nitrided refractory metal film to the antireflection film causes formation of a by-product 12, which is composed of a resist, an etching gas, and the nitrided refractory metal film serving as a base, as shown in FIG. 12, along the side surface of a contact hole when the contact hole is formed with a dry etching technique. The by-product having a shape of a crown may be left as a residue in the contact hole even after a resist ashing performed after normal etching treatment, and a resist removal process involving immersion into organic peeling solution, the by-product is thus generally called crown after its shape. Hereinafter, the by-product is referred to as crown in this specification.
The crown hinders the entrance of sputtering particles into the contact hole in the deposition of the second wiring metal film by a sputtering technique while the crown 12 is produced, disabling the deposition of a film having a desirable thickness in the inner portion of the contact hole. Therefore, as shown in FIG. 13, a wiring metal film 13 is broken to reduce a yield. When the second wiring metal film is thinly deposited at a level which does not cause a break, a problem is easily expected to become more serious in view of the reliability of the semiconductor device. However, a semiconductor device including the thin second wiring metal film passes an electrical characteristic evaluation test, so that it cannot be denied that the semiconductor device is leaked as a non-defective product to the market.
JP 05-226338 A discloses an invention in which heat treatment is performed in a nitrogen atmosphere after the deposition of the refractory metal film. Requirement for the heat treatment at the temperature of approximately 450° C., in addition to an increase in the number of process steps, leads to anxiety over increase injunction leak current by wiring metal spikes to the substrate caused by deterioration of barrier metal, which is widely used to prevent mutual diffusion between a semiconductor device substrate and a wiring metal film, and also leads to easy expectation that a thickness of the refractory metal nitride layer changes relative to that of the refractory metal film by, for example, non-uniformity in the heat treatment. In the formation of an upper-layer wiring to contact with the nitrided refractory metal layer through a contact hole, contact with the refractory metal film occurs, making it difficult to obtain a stable via resistance.
JP 05-190551 A discloses a structure having a Ti film and a TiN film which are stacked by sputtering, but in the formation of the Ti film and the TiN film in different gas atmospheres in the same processing chamber, a step of forming the TiN film by sputtering and then removing a nitride layer formed on the surface of a sputtering target by an inert gas such as Ar is required for each semiconductor substrate processing. Accordingly a processing time increases and a target material other than a target material deposited on the semiconductor substrate is also consumed, consequently cost efficiency is not preferable. In the separate formation of the Ti film and the TiN film in different processing chambers, the TiN film deposited on the inner surface of the processing chamber peels because of high stress of the TiN film, so that the peeled TiN film is more likely to fall on the semiconductor substrate to cause a pattern defect in a subsequent wiring forming step, thereby reducing the yield.